In the field of semiconductor integrated circuits, electrical conductor patterns may be deposited on the surface of an integrated circuit chip. Such conductors are used to electrically connect various integrated circuit structures within the chip and as contact pads for forming electrical connections with circuitry external to the chip. Likewise electrically resistive materials such as polycrystalline silicon may be provided on the surface of a chip to provide integrated resistors for use with the integrated circuit. Such conductors or resistors may be formed by providng a film on the surface of the chip. The film is then etched so that it is removed in all areas except for those where the conductor or resistor is to be provided. Commonly this etching is performed by what is known as a barrel or plasma etch. One etchant which may be used for such plasma etching is a mixture of CF.sub.4 and O.sub.2. This etchant is often preferred because it is safer to work with than most other etchants and less damaging both to the processing equipment and to the semiconductor materials on which the films have been formed.
Under some circumstances fluorine containing etchants cannot be used. One such circumstance is the inclusion of chromium, a common element used in such conductive or resistive films, either alone or in conjunction with other elements in the film to be etched. When chromium is used in such a film, typically a chlorine containing etchant is used. This is because the exposure of chromium to a fluorine containing plasma will tend to cause a chromium fluoride layer to form. Such a chromium fluoride layer is nonvolatile at typical etching temperatures and blocks etching. Therefore, after the chromium fluoride layer forms no further etching occurs and portions of the film which were to have been removed are only incompletely removed. Such incomplete etching causes electrical short circuits between portions of the film which were to have been retained. Furthermore chromium fluoride lacks the stability required to insure that it will not later undergo chemical changes leaving an electrically conductive residue. Therefore traces of chromium fluoride left on the chip surface could lead to undesirable electrical short circuits.